Electrical circuit.



R. V. L. HARTLEY.

ELECTRICAL CIRCUIT.

APPLICATION FILED SEPT-13.1915.

1,183,875. PatentdMay 23,1916.

To all whom it may concern:

UNITED sTArns PATENT-OFFICE;

mrn v. L. Burn r, or n'nw'ronx; n. Y., Assionon, ZBY mnsm: nssicfi mm'ro-wnsrumr nnnc'rmc cournmz, mconrom'rnn, A CORPORATION on NEW Yonx.

ELEG'IBICAL cmcum p Specification of Letters Patent.

Patented May 23, 1916.

Application fled September 18, 1915. Serial No. 50,441.

Be it known that I, RALPH Vm'r'oN LYON HARTLEY, a citizen of the UnitedStates, residing at New York, in the county of New York and State of NewYork, have invented certain new and useful Improvements, in ElectricalCircuits, of which the following is a full, clear, concise, and exactdescription.

This invention relates to electrical circuits containing amplifiers, nparticular to such circuits in which an electrical, coupling exists.which is capableof transferring ower from the output terminals of anamplifier to its input terminals. As is well known, the effect of such acoupling is to produce a tendency toward free oscillation or singing ofthe system, which is undesirable in those cases in which the network isto be used to faithfully reproduce in amlified form the power impressedu on its mput terminals. It is further well own that in some amplifiers,notably in those of the three-element audion type, such a couplingcannot be' avoided,-being due to the mutual capacity of the elements ofthe structure, and the object of this invention is,

therefore, to provide means for overcoming or neutralizing the eifect ofthis coupling, to the end that a greater amplification of input powermay be obtained without resulting instability of operation- 4 As an aidin understanding this inven 'tion, the following facts concerningamplifying networks are cited. In any amplifying network, power isintroduced into the input terminals, amplified or increased in amount,and passed out from the output terminals. If there is some electricalpath "leading from the output circuit back to the input circuit, some ofthis amplified power is again applied to the input circuit and isre-amplified. This process is then repeated and goes on without limit.It will be obvious that if the amplifying power of the repeater is solarge that the power lost by passage back from the output circuit isless than the power gained in going from input to'output circuit, anunstable condition will be set up in which the power in the outputcircuit is maintained independently of any source of power in the inputcircuit; that is,

singing is set up, in which case the system is evidently unfit for useas a repeater. The

amplification allowable before such singing takes place is, therefore,greater the less di-- rect is the connection betweencircuits; in

fact the allowable amplification is inversely proportional to the mutualimpedance of I the two circuits. It therefore follows that noslnging canoccur for any amplification whatever if this coupling is sufiicientlysmall that is, if the electromotiveforce induce in the input circuit bycurrents in the output circuit is small. Now, in the therm onic repeaterit is'impossible to eliminate this coupling, and the present inventionconnetworks containingsome such unavoidable templates introducing stillanotherelectro coupling is illustrated in the drawings,

which-,

' Figure 1 shows a typical amplifying arrangementin which an inductivecoupling of input and output circuits is secured by breaking the 'outputcircuit and closing this break through one winding of a transformer,whose other. winding is included in the input.circuit. -Fig. 2 showsanother form in which coupling is not made directly to the outputcircuit of therepeater butto' a circuit coupled to it.

In these figures the same numerals denote corresponding parts.

In Fig. 1, 1 is an incoming line or circuit, the power of which is to beaugmented; 2

.is the primary of a transformer of which 3 is the secondary, saidtransformer serving to introduce power into the amplifying system; 4 isa thermionic repeater containing filament 11, grid 12 and plate 13; 8,9, 10

are batteries for use as usual in connection with such repeaters; 14 isa high impedance choke coil which allows practically unobstructedpassage of direct current; 15 is one winding of a transformer whose,other winding is 16, the function of this transformer being to annulthat coupling of input and output-circuit which results from theassociation of elements inside the repeater itself. The action of thehigh inductance choke coil 14 is to cause the greater part of thealternating current in the'output circuitto flow electromotive forcewhose ma .phase may be adjusted b pling of the coils an .nected' in tthrorughwinding 15, thus inducing in Mi an ltude and 16. 5 isatransormerwinding in the out ut circuit of the repeater; 6, a second win ingof'the same transformer, and 7 an outgoing circuit to which power iscommunicated by-the last mentioned transformer. l

In Fig. 2 i the chokecoil 14 is shown conhe outgoing circuit 7 insteadof directl to the output circuit of the repeater.

This-c oke coil may be often omitted in either circuit arrangement,since its only function is to prevent the flow of direct current in thetransformer used for coupling input and output circuits.

n the operation of this network, an electromotive force impressed uponthe input the coupling inside circuit produces a current in the outputcircuit, which current, through the agency of the repeater, induces afurther electromotive force in the input circuit. As has been stated,the present invention consists in opposing to thelast namedelectromotive force another which is ob- -tained, in the typical casesillustrated, by

varymg the coucircuits whereby the ted to accomplish the cuit. withoutdeparting the spirit of this invention. 1

What is claimed is:;

1 .-An electrical network containing a thermionlc amplifier having aninput and an output circuit, said outputcircuit being :adjustablycoupled to said input circuit to oppose the efiect upon said inputcircuit. of

currents in said output circuit.

2. In an electrical network containing an amplifier having an input,circuit and an output circuit, said circuits being can led to produce insaid input circuit an e ect due to currents in said out ut circuit, afurther adjustable coupling '0 said circuits to oppose said efiect uponsaid input circuit.

3. In an electrical network containing a thermionic amplifier havinganinput circuit and an output circuit, a portion of said output circuitso inductively and adjustably coupled to a portion of said input circuitas to oppose in said input circuit the effect of currents in said outputcircuits.

4. In an electrical network containing a thermionic amplifier having aninput circuitand an output circuit, a transformer of adjustable mutualimpedance coupling said electromotive force induced in the input circuitby currents in the output circuit through the electrostatic coupling ofthe amplifier may be opposed by that electromotive forceinducedinsaidinput circuit by currents in said output circuit through theinductive coupling of the windings of said transformer.

In witness whereof, I hereunto subscribe 'my name this 4th day of Sept,A. D. 1915.

RALPH V. L. HARTLEY.

Witness:

P. B. LYNCH.

